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Exam 4: Knee (Biomech)

front 1

What are the knee compartments?

back 1

  1. Lateral tibiofemoral joint
  2. medial tibiofemoral joint
  3. Patellofemoral joint

front 2

2 planes of motion

back 2

  • Rarely occur without interaction from other joints of the LE
  • About 2/3 of the muscles the cross the knee also cross the hip or the ankle

front 3

Stability ___.

back 3

soft tissue restraints rather than boney anatomy

front 4

Osteology: distal femur

back 4

  • epi(condyle)= before/above
  • intracondyle: groove/notch/
    • "separate" 2 condyle (perfect match 3 patella)

front 5

Osteology: proximal tibia & fibula

back 5

  • proximal tibia: not imp, muscle attachments for biceps femoris (5% of forces)
  • epicondlye eminence: attachment for PCL and ACL
  • tibial tuberosity: attachment for quads
  • flat shape = tina plateu

front 6

Osteology: patella

back 6

  • 4-5mm of cartilage
  • facets // seismod bone
  • impede @ quad tendon

front 7

Arthrology: general considerations

back 7

  • medial hip angulation @ 125 degrees\
  • normal knee valgus: 170-175 degrees

front 8

Genu Valgum vs. Genu Varum

back 8

  • genu valgum: "gum" bwt legs
  • genu varum: bow legs // WITCH

front 9

Ligaments, fascia, and muscle table graph

back 9

  • regions of capsule
    • anterior
    • lateral
    • posterior
    • posterior-lateral
    • medial

front 10

Arthrology: general considerations, ligaments

back 10

  • knee injuries > hip injuries
    • rely on dynamic structures
  • knee = intercapsuled + extra support (MCL, LCL, PC...)
    • pes anserius tendons + hams = muscular support+stability

front 11

Arthrology: fat pads

back 11

  • synovial fluid: line inner surface, UP glide +slide,
  • knee bursa: fat pad, assist with friction-prone areas (LOWER %)
    • quads+intrapatellar

front 12

Arthrology: tibiofemoral joint

back 12

  • UP flexion+extension
  • femur on slight concave tibia (somewhat flat)
  • GOOD mvt @end ranges: tear soft tissues B4 bone damage

front 13

Arthrology: tib-fem, menisci

back 13

  • Crescent-shaped fibrocartilage structure: deepens capsule/knee
    • "stadium shaped" = hard to slide around/excessive mvts
    • quads/popliteus/semimembranosus
  • nutrients from diffusion: (red= more blood/white= none)

front 14

The menisci: an important job

back 14

  • primary function: compression absorption + increase knee surface area
  • medial side = prone to more injury b/c UP axial rotation (plant+twist_
  • MENISCUS SURGERY NOT NEEDED
    • risks with surgery = can cause early arthritis

front 15

Osteokinematics: tibiofemoral joint

back 15

  • hinge joint

front 16

Osteokinematics: flex/ext

back 16

  • tibial turberostiy moves medial: cause tibial internal rotation
  • concave condle makes axis move => change internal mvt arm of muscle
  • knee extension = closed=packed
    • more stable + more force transfer

front 17

Osteokinematics: internal & external rotation

back 17

  • internal rotation: femur shifts out
  • external rotation: femur shifts in

front 18

Arthrokinematics of tibiofemoral joint

back 18

  • tibial on femur (open chain)
    • concave on convex = SAME
    • anterior roll = anterior slide
  • femur on the tibia (closed chain)
    • convex on concave = OPPOSITE
    • anterior roll = posterior slide

front 19

screw-home mechanism

back 19

  • for full extension (w/ some Ext.R)
    • longer medial + PCL passive tension
  • popliteus IR knee = unlocking knee

front 20

Arthrokinematics of axial rotation

back 20

  • SPINNING

front 21

Medial & lateral collateral contributions

back 21

  • 2 fiber groups
  • goal: prevent valgus+valgum collapse AND some axial rotational prevention

front 22

Function of ligament and common mech. of injury chart

back 22

front 23

Anterior & posterior cruciate ligaments

back 23

front 24

The ACL

back 24

  • knee extension:
    • quads pull up + tibia kicks up + femur want to roll up
      • => keeps ACL taut
    • KEY = quad strength
  • QUADS: antagonist of ACL
  • Tear ACL: UP translation, pull on tibia (rotate foward+slide forward)
  • TEAR w/o pull: valgus, hyperextension, activate quad at flex/end range + valgus

front 25

Posterior cruciate ligament

back 25

  • checks posterior slide of knee/tibia (knee flexion)
    • most taut
  • tear PCL: tibial slides backward

front 26

The patellofemoral joint

back 26

  • stable in boney aspect
    • stabilized by quad + patella wedge in notch
  • medial +lateral femoral ligament

front 27

Patellofemoral joint kinematics

back 27

  • closed chain: femur slide under fixed patella
  • open chain: patella slide on fixed patella
  • end range flexion: tibia contact points move in k.flex = only 1/3 pf patella contact w/ mvt
    • good b/c = UP knee flexion + slide (bend/glide)
  • @90 degrees: doesn't move patella

front 28

Muscle function: extensors (aka the quads)

back 28

  • 80% of torque produced by vastus m. + 20% from rectus femoris
    • connect to quad tendon
  • extensor mechanism: quads + quad tendon + + patella
  • 66% more than knee flexors
  • isometric, concentric, eccentric

front 29

External torque demands

back 29

  • open chain: (tibia on femur)
    • more extension -> most mvt arm -> most torque
    • straight knee = larger external
  • closed chain: most mvt arm + knee flexion
    • miss squat at hole // not at top

front 30

Internal torque demands

back 30

  • max in torque @45-70 degrees of knee flexion
    • least torque @ max knee flexion + extension
  • most torque abilities
    • squat hardest @bottom + middle
    • squat easiest @top

front 31

The role of the patella

back 31

  • functional length of external mnt arm of quad
    • longest @20-30 degrees flexion
  • function: lengthens quad (spacer)
  • HIGH compression force

front 32

Patellofemoral joint kinetics

back 32

  • deep flexion: more compression (max @60-90 degrees)
    • contact area of patella + tibia @ same degrees
  • knee over tore argument: force from knee + butt
  • LOW knee bend = HIGH compression vector

front 33

Role of the quadriceps in patellar tracking

back 33

  • slight lateral pull of quads (b/c vastus): pull patella more laterally
  • Q angle: 13-15 degrees (normal)

front 34

WARNING: PATHOANATOMICS OUGHT NOT DICTATE CARE

back 34

  • pathobiomechanics/anatomy is only a part of entire picture of a human
  • procedures + paradigms NOT fully tested = adopted as standard care

front 35

Interconnectedness

back 35

  • where genu valgum originate
    • Boney: hips, knees, tibias, ankles
    • weakness: hips, ankles

front 36

Muscle function: knee flexors/rotators

back 36

  • all muscles that crosses posterior knee (NOT gastrocnemius) => flex + anterior rotate knee
    • closed chain

front 37

Control: tibial-on-femoral osteokinematics

back 37

  • hamstrings: help control tib-fib kinematics, accelerating
    • different max torque from leverages: from force-length NOT moment arm)

front 38

Maximum torque: flexors

back 38

  • force relationship
  • Max leverage: 50-90 degrees
  • Knee torque and flexion angle inverse relationship
    • HIGH knee flexion torque = LOW flexion angle (degrees)
    • LOW knee flexion torque = HIGH flexion angle